326 Journal of the Department of Agriculture. — Oct., 1922. 



THE LIFE-HISTORY OF THE WIRE-WORM OF 



SHEEP. 



Review by the Division of Veterinary Education and Research. 



/ntroductioii. — The wireworm of riuniuants, scientifically known 

 as Haem,mchus contortus, is a small thin worm which passes part of 

 its life in the "fourth stomach" or " abomasum " of sheep, cattle, 

 p'oats, and other ruminants, including' wild game such as buck. Its 

 distinguishing" scientific name contortus is given to it on account of 

 the contorted or spirnl appearance of the internal organs of the 

 female. In the adult form the white ovaries of the fonale are rolled 

 round the reddish intestine to form /eguiar loops, and this gives it a 

 spiral striping like a barber's pole. It lives by sucking blood from 

 the "mucous membrane'' or lining of the stomach, and fron) this 

 blood its intestines derive their colour. 



Post-mortem examination of an infected sheep shows the presence 

 of the adult worms, rather over an inch in length and about as thick 

 as an ordinary sewing-needle. They are found either wriggling about 

 in the stomach (abomasum) or in clusters round the stomach walls. 



The g-eneral symptoms of acute wire-worm infection are inflam- 

 mation of the stomach and " anaemia," i.e. an impoverished condition 

 of the blood. This shows itself externally as a paleness of the mucous^ 

 membranes of the mouth and eyes, loss of Hesh and general weakness, 

 accompanied by thirst and diarrhoea, and sometimes by a dropsical 

 effusion (or watery swelling*) under the iaw. 



Lambs and young sheep are most seriously affected, but altliough 

 fully-grown sheep also suffer, they can sometimes harbour the worms 

 for a long time without showing serious symptoms, provided the veld 

 is in good condition and they obtain abundance of good food. Such 

 apparently healthy adult sheep are a serious source of danger, since 

 they keep the infection alive and, in their droppings, scatter eggs to 

 infect the veld, and hence infect the rest of tlie Hock. 



There are six stages in the life-historv of the worm — the Qgg, four 

 "larval" or immature stages, and the adult. Half of these stages 

 is pas.sed in the stomach of the sheep and the other half outside on 

 the veld. The complete life-cycle may be indicated as follows: — 



Adults. — Fully-grown males and females only live in the fourth 

 stomach of sheep or other ruminants. Here they may thrive all the 

 year round, although the degree of infestation depends upon the 

 season. Once a sheep is infected with M'ire-worms it may remain 

 infected for a very long time unless measures are taken to (a-adicate 

 the parasite. 



The female is somewhat larger than the male, and is readily 

 distinguished by the enlargement over the hind third of its length, 

 corresponding to the egg-laying organs. AVhen full size has been 

 reached, the average length is about one inch and the riverage breadth 

 about one-fiftieth part of an inch. The females are theu fertilized by 

 the males and egg-laying begins. 



Eggs. — The eggs then leave the stouiacli along with the food, pass- 

 through the intestines, and out with the drojjpings or " faeces." The 



